<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src="https://unpkg.com/vue@3/dist/vue.global.js"></script>
</head>

<body>
    <div id="app"></div>

    <template id="my-app">
        <input ref="name">
        {{}}
    </template>

    <script>
        const App = {
            template: "#my-app",
            data() {
                return {

                }
            },
            mounted() {
                this.$refs.name.focus()
            }
        }
        Vue.createApp(App).mount('#app')
    </script>
</body>

</html>